Lean Body Mass Calculator
Estimate your lean body mass (LBM) — total weight minus body fat — using multiple established formulas.
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About Lean Body Mass
Lean body mass (LBM) is the total weight of your body minus all fat mass. It includes muscles, bones, organs, skin, blood, and water — everything except stored fat.
How LBM is calculated
This calculator uses three established formulas for adults and one for children:
- Boer (1984): Male: 0.407W + 0.267H − 19.2. Female: 0.252W + 0.473H − 48.3. W = weight in kg, H = height in cm.
- James (1976): Male: 1.1W − 128(W/H)². Female: 1.07W − 148(W/H)².
- Hume (1966): Male: 0.3281W + 0.3393H − 29.53. Female: 0.2957W + 0.4181H − 43.29.
- Peters (children ≤ 14): Uses estimated extracellular volume: eECV = 0.0215 × W0.6469 × H0.7236, then LBM = 3.8 × eECV.
Why LBM matters
Knowing your lean body mass helps you track muscle gain or loss over time, set realistic body composition goals, and calculate more accurate calorie needs (e.g. the Katch-McArdle BMR formula uses LBM).
Tips
- Measure height without shoes and stand straight.
- Use a recent weight measurement taken under consistent conditions (same time of day, similar clothing).
- These are estimates — for precise body composition, consider DEXA scanning or hydrostatic weighing.